There are many types of prior art wall decorating systems such as paint and/or wallpapering. Both paint and wallpaper, however, are permanent and are not reusable. To significantly change the appearance of a painted or wallpapered wall, the wall typically is repainted or wallpapered with a different wallpaper or paint. Such processes are generally expensive and time consuming. Additionally, paint is messy to apply and wallpaper is difficult to install.
U.S. Pat. No. 4,900,604 to Martinez et al. (the entire contents of which are herein incorporated by reference) is directed to adhesive wall decorating systems previously sold under the name "Decorate-It!".TM. Room Decorating System. That system comprises substrate or "backing" sheets and a plurality of pre-cut self adherent appliques. The backing sheets and appliques are coated with a repositionable adhesive to afford rearrangement of the appearance of a wall or other surface by changing the relative positions of the backing sheet and appliques.
The appliques and backing sheets described in Martinez et al. were constructed from a thin film or sheet of flexible material, such as plasticized polyvinyl chloride (PVC) based material. The film should be conformable to adjust to irregularities and discontinuities in substrates such as light switch frames along wall surfaces or irregularly textured surfaces.
Conformance as discussed in this case has two basic elements. First, the film must be capable of initially modifying its shape so that it will accommodate irregular surfaces over which it is stretched FIG. 6A illustrates a thin film 2 having an adhesive 3 coated over one side that adheres the film 2 to an irregular substrate or surface 4, such as a wallpapered or painted wall. Initially, PVC films are highly conformable and may conform to an irregular surface.
The ability of a film to initially conform over an irregular surface can be measured by evaluating the hysteresis of the film. Hysteresis is a measurement of the energy lost or dissipated during cyclic deformation of a film sample. The greater the amount of energy lost (hysteresis), the more conformable the film. While PVC films exhibit excellent initial hysteresis properties, they suffer other drawbacks as will be illustrated below. Unfilled ionomeric polymer-based films generally have unacceptably low hysteresis values. Because they do not provide good initial conformance to irregular surfaces, unfilled ionomeric-polymer films are not desirable.
The second important element to conformance as described herein is the Long-Term Elastic Recovery of the film. Long-Term Elastic Recovery is discussed below in the detailed description of the preferred embodiment. Polyvinyl chloride (PVC) films used to construct the appliques and backing sheets described in Martinez et al. are highly plasticized to give them flexibility for use as appliques and backing sheets. The PVC is typically processed by premixing in plasticizers and stabilizers, then sheeting out the film in a calendering operation. When the film is laminated to a liner, the film is held in a stretched conformation that is only released when the film is removed from the liner. In later use, such as when the backing sheets or appliques are applied to a wall or other surface, the film may be additionally manually stretched. After time passes, the film "remembers" its relaxed state; and the film typically shrinks or contracts, particularly at elevated temperatures.
FIG. 6B illustrates the relationship between a substrate 4 and an adhesive coated PVC film 2 after time has passed. The film 2 remembered its relaxed state and shrank or contracted. Shrinkage of the polyvinyl chloride (PVC) based appliques and backing sheets contributes to adhesive shear failure resulting in separation between the appliques, backing sheets and the substrate (e.g. the backing sheet or applique falling off the wall). This phenomenon is illustrated in FIG. 6B which shows reduced contact between the adhesive 3 and the irregular surface 4. The reduced surface area of adhesive 3 and surface 4 in contact results in increased stress in the adhesive layer 3 that tends to result in the film 2 and adhesive 3 separating from the surface 4 (e.g. the applique or backing sheet falling off the wall).
Additionally, over time, plasticizers or other additives for polyvinyl chloride (PVC) based materials tend to migrate or leach from the bulk material resulting in a general degeneration of mechanical properties such as embrittlement and reduced flexibility. Also, polyvinyl chloride (PVC) based materials generally release chlorinated by-products during combustion.
Ionomeric resins (such as the Surlyn.upsilon. family of resins, commercially available from E. I. DuPont de Nemours Co.) have been mainly exploited as a tough covering for sporting equipment such as golf balls, and as a heat-shrinkable plastic wrap component. In some cases, the cold temperature properties of ionomers have proved useful, as in U.S. Pat. No. 4,161,562. Ethylene-co-methacrylic acid copolymers have been blended, as in U.S. Pat. Nos. 3,445,546 and 3,869,422, and more recently U.S. Pat. No. 4,916,025. In the latter patent, Surlyn.TM. material was used only as a heat sealing outer layer, optionally blended with other resins to reduce cost. Given the recommended uses for Surlyn.TM. resins, one would not expect the filled material to act as a stand-alone conformable film.
U.S. Pat. No. 4,279,344 describes a peelable, heat-sealable packaging laminate. The inner sealing layer is formed from polypropylene or polyethylene/polypropylene copolymer blended with 15-35% Surlyn.TM. ionomer. The heat-sealed Surlyn.TM. film bonds are described as hand peelable.
U.S. Pat. No. 4,835,025 describes a barrier laminate for essential oils/flavorings composed of paper substrate coated with nylon, which is coated with Surlyn.TM. resin and a coating of olefin (polyethylene) overall. The intermediate nylon or Surlyn.TM. film layer may be pigmented using a pigment such as TiO.sub.2 at 0.5-15%.
U.S. Pat. No. 4,653,752 describes a sport ball comprised of a plastic shell covered with a sewn cover. The shell is a blend of Surlyn.TM. resin with 25-50% ethylene-co-vinyl acetate (EVA). The Surlyn.TM. resin is described as providing strength and durability, while the EVA provides softness. These properties are noted for bulk-like materials such as spherical balls. Increasing EVA content leads to more rubbery, softer materials, while increasing Surlyn.TM. resin levels leads to harder, more resilient materials. With respect to additives, small amounts of other plastic polymers may be added without changing the characteristics significantly, and glass may be added as well.